The first catalytic asymmetric (4+3) cyclization of in situ generated ortho‐quinone methides with 2‐indolylmethanols has been established, which constructed seven‐membered heterocycles in high yields ...(up to 95 %) and excellent enantioselectivity (up to 98 %). This approach not only represents the first catalytic asymmetric (4+3) cyclization of o‐hydroxybenzyl alcohols, but also enabled an unprecedented catalytic asymmetric (4+3) cyclization of 2‐indolylmethanols. In addition, a scarcely reported catalytic asymmetric (4+3) cyclization of para‐quinone methide derivatives was accomplished.
The first catalytic asymmetric (4+3) cyclization of in situ generated ortho‐quinone methides with 2‐indolylmethanols was developed, and was used to construct seven‐membered heterocycles in high yields and excellent enantioselectivity. This approach represents the first catalytic asymmetric (4+3) cyclization of o‐hydroxybenzyl alcohols, and also enabled the unprecedented catalytic asymmetric (4+3) cyclization of 2‐indolylmethanols.
Sodium‐ion batteries capable of operating at rate and temperature extremes are highly desirable, but elusive due to the dynamics and thermodynamics limitations. Herein, a strategy of ...electrode–electrolyte interfacial chemistry modulation is proposed. The commercial hard carbon demonstrates superior rate performance with 212 mAh g−1 at an ultra‐high current density of 5 A g−1 in the electrolyte with weak ion solvation/desolvation, which is much higher than those in common electrolytes (nearly no capacity in carbonate‐based electrolytes). Even at −20 °C, a high capacity of 175 mAh g−1 (74 % of its room‐temperature capacity) can be maintained at 2 A g−1. Such an electrode retains 90 % of its initial capacity after 1000 cycles. As proven, weak ion solvation/desolvation of tetrahydrofuran greatly facilitates fast‐ion diffusion at the SEI/electrolyte interface and homogeneous SEI with well‐distributed NaF and organic components ensures fast Na+ diffusion through the SEI layer and a stable interface.
In a THF‐based electrolyte with a weak solvation structure, Na+ desolvation is fast and a uniform solid electrolyte interphase (SEI) with abundant NaF and organic compounds is generated on the commercial hard carbon anode. This greatly enhances the interface stability and enables the rapid migration of Na+ in the SEI, thus realizing the high rate capability, long‐term stability and good low‐temperature performance for the hard carbon anode.
By using copper(I) homoenolates as nucleophiles, which are generated through the ring‐opening of 1‐substituted cyclopropane‐1‐ols, a catalytic asymmetric allylic substitution with allyl phosphates is ...achieved in high to excellent yields with high enantioselectivity. Both 1‐substituted cyclopropane‐1‐ols and allylic phosphates enjoy broad substrate scopes. Remarkably, various functional groups, such as ether, ester, tosylate, imide, alcohol, nitro, and carbamate are well tolerated. Moreover, the present method is nicely extended to the asymmetric construction of quaternary carbon centers. Some control experiments argue against a radical‐based reaction mechanism and a catalytic cycle based on a two‐electron process is proposed. Finally, the synthetic utilities of the product are showcased by means of the transformations of the terminal olefin group and the ketone group.
A catalytic asymmetric allylic substitution with NHC‐stabilized copper(I) homoenolates generated from cyclopropanols is developed that affords γ‐chiral ketones in excellent regio‐ and high enantioselectivities. This process enables the generation of chiral quaternary carbon centers and features a broad substrate scope.
A path-factor is a spanning subgraph
F
of
G
such that every component of
F
is a path with at least two vertices. Let
k
≥ 2 be an integer. A
P
≥
k
-factor of
G
means a path factor in which each ...component is a path with at least
k
vertices. A graph
G
is a
P
≥
k
-factor covered graph if for any
e
∈
E
(
G
),
G
has a
P
≥
k
-factor including
e
. Let
β
be a real number with
and
k
be a positive integer. We verify that (i) a
k
-connected graph
G
of order
n
with
n
≥ 5
k
+ 2 has a
P
≥3
-factor if ∣
N
G
(
I
)∣ >
β
(
n
−3
k
− 1) +
k
for every independent set
I
of
G
with ∣
I
∣ = ⌊
β
(2
k
+ 1)⌋; (ii) a (
k
+ 1)-connected graph
G
of order
n
with
n
≥ 5
k
+ 2 is a
P
≥3
-factor covered graph if ∣
N
G
(
I
)∣ >
β
(
n
− 3
k
− 1) +
k
+ 1 for every independent set
I
of
G
with ∣
I
∣ = ⌊
β
(2
k
+ 1)⌋.
A fractional
a, b
-factor of a graph
G
is a function
h
from
E
(
G
) to 0, 1 satisfying
a
≤
d
G
h
(
v
)
≤
b
for every vertex
v
of
G
, where
d
G
h
(
v
)
=
∑
e
∈
E
(
v
)
h
(
e
)
and
E
(
v
) = {
e
=
uv
...:
u
∈
V
(
G
)}. A graph
G
is called fractional
a, b
-covered if
G
contains a fractional
a, b
-factor
h
with
h
(
e
) = 1 for any edge
e
of
G
. A graph
G
is called fractional (
a, b, k
)-critical covered if
G
—
Q
is fractional
a, b
-covered for any
Q
⊆
V
(
G
) with ∣
Q
∣ =
k.
In this article, we demonstrate a neighborhood condition for a graph to be fractional (
a, b, k
)-critical covered. Furthermore, we claim that the result is sharp.
Cyclosporin A (CsA) is a promising therapeutic drug for myocardial ischemia reperfusion injury (MI/RI) because of its definite inhibition to the opening of mitochondrial permeability transition pore ...(mPTP). However, the application of cyclosporin A to treat MI/RI is limited due to its immunosuppressive effect to other normal organ and tissues. SS31 represents a novel mitochondria-targeted peptide which can guide drug to accumulate into mitochondria. In this paper, mitochondria-targeted nanoparticles (CsA@PLGA-PEG-SS31) were prepared to precisely deliver cyclosporin A into mitochondria of ischemic cardiomyocytes to treat MI/RI.
CsA@PLGA-PEG-SS31 was prepared by nanoprecipitation. CsA@PLGA-PEG-SS31 showed small particle size (~ 50 nm) and positive charge due to the modification of SS31 on the surface of nanoparticles. CsA@PLGA-PEG-SS31 was stable for more than 30 days and displayed a biphasic drug release pattern. The in vitro results showed that the intracellular uptake of CsA@PLGA-PEG-SS31 was significantly enhanced in hypoxia reoxygenation (H/R) injured H9c2 cells. CsA@PLGA-PEG-SS31 delivered CsA into mitochondria of H/R injured H9c2 cells and subsequently increased the viability of H/R injured H9c2 cell through inhibiting the opening of mPTP and production of reactive oxygen species. In vivo results showed that CsA@PLGA-PEG-SS31 accumulated in ischemic myocardium of MI/RI rat heart. Apoptosis of cardiomyocyte was alleviated in MI/RI rats treated with CsA@PLGA-PEG-SS31, which resulted in the myocardial salvage and improvement of cardiac function. Besides, CsA@PLGA-PEG-SS31 protected myocardium from damage by reducing the recruitment of inflammatory cells and maintaining the integrity of mitochondrial function in MI/RI rats.
CsA@PLGA-PEG-SS31 exhibited significant cardioprotective effects against MI/RI in rats hearts through protecting mitochondrial integrity, decreasing apoptosis of cardiomyocytes and myocardial infract area. Thus, CsA@PLGA-PEG-SS31 offered a promising therapeutic method for patients with acute myocardial infarction.
At moderate temperatures (≤ 70°C), thermal reduction of graphene oxide is inefficient and after its synthesis the material enters in a metastable state. Here, first-principles and statistical ...calculations are used to investigate both the low-temperature processes leading to decomposition of graphene oxide and the role of ageing on the structure and stability of this material. Our study shows that the key factor underlying the stability of graphene oxide is the tendency of the oxygen functionalities to agglomerate and form highly oxidized domains surrounded by areas of pristine graphene. Within the agglomerates of functional groups, the primary decomposition reactions are hindered by both geometrical and energetic factors. The number of reacting sites is reduced by the occurrence of local order in the oxidized domains, and due to the close packing of the oxygen functionalities, the decomposition reactions become - on average - endothermic by more than 0.6 eV.
Composites of transition metal and carbon-based materials are promising bifunctional catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and are widely used in ...rechargeable metal–air batteries. However, the mechanism of their enhanced bicatalytic activities remains elusive. Herein, we construct N-doped graphene supported by Co(111) and Fe(110) substrates as bifunctional catalysts for ORR and OER in alkaline media. First-principles calculations show that these heterostructures possess a large number of active sites for ORR and OER with overpotentials comparable to those of noble metal benchmark catalysts. The catalytic activity is modulated by the coupling strength between graphene and the metal substrates, as well as the charge distribution in the graphitic sheet, which is delicately mediated by N dopants. These theoretical results uncover the key parameters that govern the bicatalytic properties of hybrid materials and help prescribe the principles for designing multifunctional electrocatalysts of high performance.
▶ Lithium bis(fluorosulfonyl)imide (LiFSI) has been studied as conducting salt for nonaqueous liquid electrolytes for lithium-ion batteries. ▶ Lithium bis(fluorosulfonyl)imide (LiFSI) exhibits far ...superior stability towards hydrolysis than lithium hexafluorophosphate (LiPF
6) and does not release hydrogen fluoride (HF). ▶ Pure lithium bis(fluorosulfonyl)imide (LiFSI) does not corrode Al, and Al corrosion is induced by trace amounts of chloride (Cl
−) impurities present in it. ▶ Lithium bis(fluorosulfonyl)imide (LiFSI) outperforms lithium hexafluorophosphate (LiPF
6) for lithium-ion batteries.
Lithium bis(fluorosulfonyl)imide (LiFSI) has been studied as conducting salt for lithium-ion batteries, in terms of the physicochemical and electrochemical properties of the neat LiFSI salt and its nonaqueous liquid electrolytes. Our pure LiFSI salt shows a melting point at 145
°C, and is thermally stable up to 200
°C. It exhibits far superior stability towards hydrolysis than LiPF
6. Among the various lithium salts studied at the concentration of 1.0
M (=
mol
dm
−3) in a mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7, v/v), LiFSI shows the highest conductivity in the order of LiFSI
>
LiPF
6
>
LiN(SO
2CF
3)
2 (LiTFSI)
>
LiClO
4
>
LiBF
4. The stability of Al in the high potential region (3.0–5.0
V vs. Li
+/Li) has been confirmed for high purity LiFSI-based electrolytes using cyclic voltammetry, SEM morphology, and chronoamperometry, whereas Al corrosion indeed occurs in the LiFSI-based electrolytes tainted with trace amounts of LiCl (50
ppm). With high purity, LiFSI outperforms LiPF
6 in both Li/LiCoO
2 and graphite/LiCoO
2 cells.
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